Fluid operated press construction



g- 1952 A. M DONALD 2,608,064

FLUID OPERATED PRESS CONSTRUCTION I Filed July 25, 1949 2 SHEETSSHEET l INVEN TOR.

Afro/MAG Aug. 26, 1952 MCDONALD 2,608,064

FLUID OPERATED PRESS CONSTRUCTION Filed July 25, 1949 2 SHEETSSHEET 2 IIITI S JNVENTOR. ANGUS W 004 440 BY wemi/vwyw Arroe/vzrs Patented Aug. 26, 1952 FLUID OPERATED PRESS CONSTRUCTION Angus McDonald, Pontiac, Mich., assignor to Baldwin Rubber Company, Pontiac, Mich., a

corporation of Michigan Application July 25, 1949, Serial No. 106,593

3 Claims.

This invention relates generally to presses and refers more particularly to presses of the type wherein the platen provides a backing for the work supporting plate during the operation of the press.

In certain types of presses, it is customary to move the platen downwardly against the work carrying plate, and to subsequently move the work carrying plate upwardly by a fluid pressure operated diaphragm with suflicient force to perform the desired press operation. The upward thrust applied to the work carrying plate by the diaphragm is ordinarily of substantial magnitude, and the effectiveness of the pressing operation frequently depends on the ability of the platen to withstand the shock of this thrust without moving upwardly. The problem of holding the platen against upward displacement by the action of the diaphragm during the press operation is especially critical in instances where the platen is of the floating type and moves downwardly by the action of gravity. Mechanical latch mechanisms may be provided for holding the platen against upward travel, but such devices are usually complicated, and furthermore, do not adapt themselves to holding the platen against upward movement from difierent elevated positions.

With the above in view it is one of the objects of this invention to hold the platen against upward movement during the press operation by a confined column of a relatively non-compressible fluid medium which may be readily released subsequent to the press operation to enable upward movement of the platen. In accordance with this invention a cylinder is supported above the platen with its axis extending vertically and a piston is slidably supported in the cylinder. The piston is connected to the platen for operating the latter, and a reservoir containing a supply of a relatively non-compressible fluid medium communicates with the upper end of the cylinder through a passage. The arrangement is such that downward movement of the piston in the cylinder draws fluid into the space in the cylinderabove the piston from the reservoir at a rate determined to maintain this space filled with the relatively non-compressible fluid throughout the entire downward travel of the piston.

It is another object of this invention to control the passage extending from the reservoir to the cylinder by a valve movable to close the passage subsequent to movement of the platen against the work carrying plate and thereby trap the fluid in the cylinder above the piston. Since the fluid medium trapped in the cylinder above the piston is relatively non-compressible, the platen is firmly held against upward displacement by the action of the diaphragm.

The valve is opened subsequent to the press operation to open the passage, and the platen is moved upwardly by introducing fluid under pressure into the cylinder below the piston. During upward movement of the piston the relatively non-compressible fluid in the cylinder above the piston is displaced by the latter through the passage back into the reservoir.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a semi-diagrammatic elevational view of a diaphragm press having a fluid lock embodying the features of this invention;

Figure 2 is a vertical sectional view through the fluid locking unit; and

Figure 3 is a diagrammatic view showing the shuttle valve of the locking unit and the means for operating the same.

Briefly this invention concerns itself with means for holding a platen against retracting movement by a relatively non-compressible fluid such as oil or similar liquids, and has many diversified applications. However, for the purpose of illustration the hydraulic lock for the platen is shown as applied to a diaphragm operated press wherein the platen acts as a backin and takes the shock resulting from operation of the diaphragm without movement. Such presses are especially suitable for use in instances requiring the application of a short, sudden stroke of considerable force on the work and are extensively employed for shearing or cutting sheets of stock to a preselected shape. For example, in the manufacture of certain types of rubber or rubberlike mats, it is necessary to trim the sheets to the required size, and the invention about to be described in detail is highly suitable for this purpose.

The invention may be used in connection with any one of a number of different types of diaphragm presses or their equivalents, and the detailed construction of the press forms no part of this invention. It will sufiice to point out that the press comprises a base assembly l0 and a platen I l The base assembly has a bottom part I2 which forms a chamber for fluid such as air under pressure, and has a diaphragm l3 supported on the top of the bottom part in a position to form the top wall of the chamber. The marginal edge portions of the diaphragm are clamped to the bottom part |2 by a frame section |4 suitably secured to the part l2 and serving as a retainer for the work supporting plate |5. The bottom of the plate l5 engages the central portion of the diaphragm l3, and is movable vertically relative to the frame M. In instances where the press is used for the purpose of trimming sheet stock, a shearing frame or fixture I6 is suitably secured to the top of the plate l5 in a position to enable placing a sheet of stock over the fixture, as diagrammatically shown in Figure 1 of the drawings. As will be presently described the platen is supported directly above the plate l5, and is movable to a position wherein it forms a backing for the work supporting plate l5. When the platen is in the above position fluid under pressure is admitted to the chamber in the part l2 beneath the diaphragm l3, and the latter applies an upward thrust on the plate l5. stock on the plate |5 is pressed against the platen H, and is sheared or trimmed by the fixture I6. The air under pressure is supplied to the chamber in the part l2 from a suitable source (not shown) through a conduit I! and a valve. IS. The operation of the valve I8 to alternatively connect the chamber to the source of air under pressure and to an exhaust may be accomplished electrically by suitable timing equipment, not shown.

The platen H is movable by the action of gravity in a downward direction against the worlr supporting plate l5, and is effectively held in a stationary position during the press operation by what may be termed a fluid or hydraulic lock embodying the mechanism designated. generally on the drawings by the numeral 20. In detail the mechanism embodies a cylinder 2| suitably supported above the platen II with its axis extending vertically and having the lower end closed by a plate 22 securedin place by studs 23. The plate 22 is centrally apertured to receive a rod 24 having the lower end secured to the platen H and having the upper end secured to a piston.

25, which is slidably supported inthe cylinder 2|. The escape of fluid from the interior of the cylinder 2| through the joint between the bottom plate 22 and the lower end of the cylinder is prevented by an O-ring seal 26. Also fluid from the interior. of the cylinder is prevented from escaping. along the rod 24 by a packing ring type seal 2'! suitably secured to the plate 22 and slidably engaging the rod 24. The escape of fiuid in either direction past the piston 25 is prevented by a pair of rings 28 respectively clamped against opposite ends of the piston by clamping 1-ings29 andstuds 30'. terial, and are provided with annular axially extending flanges 3| at the periphery thereof. The flanges 3| extend in opposite directions away from the piston and frictionally engage the inner wall of the cylinder. Thus regardless of whether the piston is moved upwardly Or downwardly in the cylinder, fluid is prevented from escaping past the piston. In order to assure effectively sealing the space in the cylinder at opposite sides of the piston from one another, a plurality of sealing rings 32 of the expansible type may also be provided. The rings 32. are respectively sup ported in annular grooves 33 formed in the outer wall of the piston 25 between the rings 28, and are spaced from each other in the direction of the axis of the piston. It will be noted that the upper end of the rod 24 is reduced and extends through a central opening in the piston 25. The piston 25 is secured against the shoulder 34 formed by the reduced upper end of the rod 24 Thus the The rings 28 are formed of a flexible. ma.-

by a clamping nut 35, and an O-ring seal 36 is provided on the reduced upper end of the rod to prevent fluid from escaping in either direction along the portion of the rod which extends through the piston. It follows from the above that the space in the cylinder 20 below the piston 25 is efiectively sealed from the space in the cylinder above the piston, and the reason for this arrangement will become apparent as this description proceeds.

The upper end or" the cylinder 2| is closed by a plate 3'! suitably secured in place by studs 38 and having an annular recess 39 in the bottom surface for accommodating an O-ring seal 40. The O-ring seal 40 engages the top of the cylinder .28. around the opening through the upper end thereof, and prevents the escape of fluid from the upper end of the cylinder.

A reservoir 4| is positioned above the plate 31, and is secured to the plate by suitable studs 42. The reservoir is adapted to contain a supply of relatively non-compressible fluid, such for example, as oil, and the capacity of the reservoir is somewhat greater than the volume of the space in the cylinder 2| above the piston 25 when the latter is in its lowermost position in the cylinder. The topwall 43 of the reservoir has a suitable filler opening 44, and is also provided with a bleeder cap 45- which communicates with the atmosphere in. order to provide atmospheric pressure Within the reservoir. If desired a suitable sight glass 46 may be secured to one side of the reservoir in order to illustrate the level of the fluid medium contained in the reservoir.

The plate 31 forms the bottom wall of the reservoir 4|, and is fashioned to provide a cylinder 41 having its axis extending normal to the axis of the cylinder 2|. As shown in Figure 2 of the drawings, the plate 31 has two ports 48 and 49. The port 48 communicates with the reservoir, and thev port 49 communicates with the interior of the cylinder 2| at a point above the piston. 25'. The two ports cooperate with the cylinder 4''! in forming a passage 50 between the in- I terior of the reservoir 4| and the upper end of the. cylinder 2|.

The flow of fluid medium from the. reservoir 4| into the upper end of the cylinder 2| is controlled by a shuttle valve member 5| slidably supported in the cylinder 41, and having axially spaced enlargements 52 and 53. In one position of the shuttle valve member the enlargement 52 closes the passage 50', and in another position of the. valve member 5|, communication is established through the passage 50 around the reduced portion of the shuttle valve between the enlargements.

The shuttle valve member 5| is movable to the above positions by an air cylinder diagrammatically shown in Figure 3 by the numeral 54. The air cylinder has a piston 55 which is connected to the shuttle valve by a rod 56. The opposite ends of the air cylinder 54 are alternatively connected to a source of fluid under pressure, and a suitable exhaust by a four-way valve 51. The four-way valve 51 may be electrically operated by a solenoid 58 electrically connected in the timing circuit (not shown) so as to be operated in timed relation with the valve 8.

The space in the cylinder 2| below the piston 25 communicates with a passage 60 formed in the bottom plate 22 and suitably connected to a source of fluid such as air under pressure through the medium of a three-way valve 5|. The three-way valve 6| is also preferably electrically operated by the timing circuit in order to function in proper relationship to the valves 5| and I8. The purpose of the valve 6| isto alternatively connect the lower end of the cylinder 2| tothe source of air under pressure, and to an exhaust; The sequence of operation of the valves I8; 5| and GI by the timing or other suitablemechanism will be clearly understood upo considering the following description.

Operation When the platen is in its uppermost position, the valve 6| is opened to connect the lower end of the cylinder 2| to the source of air under pressure, and the piston 25 is supported in its uppermost position shown in Figure 2 of the drawings by the pressure of the air in the cylinder 2| below the piston. Also in the above position of the platen H, the shuttle valve 5| is in the position thereof shown in Figure 2 of the drawings, wherein communication is established between the reservoir 4| and the upper end of the cylinder 2| through the passage 50. As a result the fluid medium contained in the reservoir is free to flow through the passage 50 into the upper end of the cylinder 2|.

Assuming now that a sheet of stock to be trimmed is supported on the plate I5 over the fixture I6, and that it is desired to trim this stock, the three-way valve 6| is operated to connect the lower end of the cylinder or passage 60 to a suitable exhaust. As a result of the drop in pressure in the cylinder 2| below the piston 25, the latter together with the platen is moved downwardly by the action of gravity until the platen rests against the sheet of stock. During the downward movement of the piston 25, fluid from the reservoir flows downwardly through the passage 50 into the upper end of the cylinder 2|, and fills the space in the cylinder 2| above the piston, so that a solid column of relatively non-compressible fluid exists between the top of the piston and the reservoir. The four-way valve 51 is then operated to in turn move the shuttle valve 5| to a position wherein the enlargement 52 closes the passage 5|], and traps the fluid medium in the upper end of the cylinder. Immediately after the shuttle valve 5| is operated to close the passage 50, the valve I8 is operated to admit fluid under pressure into the part l2 below the diaphragm l3. As a result the central portion of the diaphragm I3 is moved upwardly with considerable force, and the plate I5 is thrust against the platen II to enable the trimming fixture IE to shear or trim the sheet of stock. The thrust applied to the platen by the diaphragm I3 is transmitted to the column of relatively non-compressible fluid above the piston, and since the shuttle valve 5| is closed, thi column of fluid positively holds the platen against upward displacement. Immediately following the completion of the trimming operation, the valve I8 operates to exhaust the air under pressure in the part l2, and the shuttle valve 5| is moved to its open position. Also the three-way valve 6| is operated to again connect the lower end of the cylinder to the source of fluid under pressure. As a result the piston 25 is moved upwardly in the cylinder 2| and the relatively non-compressible fluid medium in the cylinder above the piston is displaced by the latter through the passage 50 into the reservoir 4 I.

It follows from the above that the platen is held in a position against the work carrying plate |5 regardless of the location of the piston 25 within the cylinder, and as a consequence, variations in the. elevation of the work supporting plate or fixture It are automatically compensated for without the necessity of providing complicated mechanical or other types of adjustments. It will also be noted that the piston is efiectively sealed, so that the hydraulic fluid medium and the air pressure at opposite sides of the piston cannot escape past the piston during operation of the latter. In this connection attention is again directed to Figure 2 of the drawings, wherein it will be noted that the interior of the cylinder 41 at opposite ends of the enlargements 52 and 53 are respectively connected to the interior of the reservoir 4| adjacent the top of the latter by vertical tubes 65. These tubes serve to equalize the pressure in the cylinder 41 and reservoir 4|, so that there is very little tendency for leaks to develop.

What I claim as my invention is:

1. A press having in combination a cylinder supported with its axis extending vertically, a piston supported in the cylinder for reciprocation, a platen positioned below the lower end of the cylinder and connected to said piston for operation by the latter, a reservoir for a relatively non-compressible fluid medium supported above the cylinder and having a fluid connection with the upper end of the cylinder whereby fluid flows by the action of gravity from the reservoir into the space in the cylinder above the piston, valve means for opening and closing the fluid connection between the reservoir and upper end of the cylinder, said valve controlled fluid connection constituting the sole communication between the reservoir and cylinder so that in the closed position of the valve means the fluid medium is trapped in the cylinder above the piston and movement of the latter upwardly is definitely blocked.

2. A press having in combination a platen, a cylinder, a piston slidably supported in said cylinder, a connection between said piston and platen for moving the latter by said piston, a

reservoir for a relatively non-compressible fluid medium having a fluid connection with said cylinder for supplying fluid to said cylinder in back of said piston as the latter moves in one direction, valve means for opening and closing the fluid connection between said reservoir and cylinder, said valve controlled fluid connection constituting the sole communication between said reservoir and cylinder so that in the closed position of said valve means the fluid medium is trapped in said cylinder and movement of said piston in the opposite direction is definitely blocked.

3. In a press of the diaphragm type having a base assembly and a platen mounted in superimposed relation for up and down movement toward and away from each other, the combinationof a vertically disposed cylinder supported above the platen, a piston supported in said cylinder for reciprocation and connected at its lower end to the platen for up and down movement of the latter by said piston, a reservoir for a relatively non-compressible fluid medium having a fluid connection with the upper end of said cylinder for supplying the fluid medium to the space in said cylinder above said piston as the latter moves downwardly to move the platen toward the base assembly, valve means for opening and closing said fluid connection between said reservoir and the upper end of said cylinder, said valve controlled connection constituting the sole communication between said reservoir and cylinder REFERENCES CITED The following references are of record in the 10 fife of this patent:

UNITED STATES PATENTS Number Name Date Leavitt May 1'7, 1898 Craig Apr. 12, 1927 Ernst et' a1. Aug. 9, 1932 MacMillin Oct. 25, 1932 Ernst et a1. Feb. 28, 1933 Stanley Sept. 5, 1939 Dinzl Nov. 5, 1940 Conzelman Oct. 15, 1946 

